package com.cy1;

import java.util.HashMap;

public class MapDemo {
    public static void main(String[] args) {
        HashMap<String, Integer> m = new HashMap<>();
        m.put("chenyong",25);
        Integer c = m.get("chenyong");
        m.clear();
        System.out.println(m.size());
        System.out.println(c);

    }


}
